# 27 W/hr-battery, means 7 hr notebook life?

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I see that Dell's new X1 notebook has a 3-cell 27 W/hr-battery. If I
assume voltage is 15v and current is 4A, then it consumes 15/4=3.75W.

27/3.75= 7.2 hrs. I guess this can't be actual battery time?

## Re: 27 W/hr-battery, means 7 hr notebook life?

Sounds about right. Since it's really just a Samsung Q30, i would skip
the middleman and save yourself some nightmares.

--------
AJ

## Re: 27 W/hr-battery, means 7 hr notebook life?

Jan wrote:

Power = volts * amps.  P = 15*4 = 60 watts. Energy = Power * time : time
= energy/power = 27 watt-hr/60 watt = 0.45 hours.  This doesn't fly
since the assumption of 4amps continuous load is wrong and the 15 volts
could well be only the overvoltage required for battery charging.

You really have to work this the other way around on the basis of a
total system work cycle, taking into account the performance
characteristics of each device on the system: hd, optical drive,
display, cpu, ram, etc for a schedule of user functions on the laptop.

Q

Huh?

## Re: 27 W/hr-battery, means 7 hr notebook life?

Without doing the math a 27 Watt hour battery would run your laptop about 1
hour.

## Re: 27 W/hr-battery, means 7 hr notebook life?

It's 15 volts, and if the current is 4 amps, that is 60 watts, or 60
watt-hours per hour.  A 27 watt hour battery would be exhausted in less
than 30 minutes.  Something's wrong here, but it's not my calculations
(I'm a degreed EE and an FCC license Amateur Radio Operatior and
Broadcast Engineer for over 40 years).

Gary Helfert wrote:

## Re: 27 W/hr-battery, means 7 hr notebook life?

I believe the battery is actutally rated 27W-hr, not Watts/hr. and you are
correct 15V @ 4 amps equates to 60 watts, however this is the maximum
expected power. It assumes there may be times you are making full use of